The invention relates to improvements in methods and apparatus for treating tobacco, and more particularly to improvements in methods of and in apparatus for homogenizing inhomogeneous accumulations (particularly piles, stacks or streams) of tobacco parts.
A mixture of tobacco parts which are to be processed into the fillers of cigarettes or into other smokers' products can contain a large number of (up to thirty) different tobacco parts. Tobacco parts can be classified in a number of different ways, such as by origin (e.g., Burley, Virginia and Oriental), by previous treatment (e.g., with or without flavoring agents), by size (such as tobacco leaf laminae and tobacco ribs or stem), by quality (such as natural tobacco leaves, fragments of foils or sheets of reconstituted tobacco and substitute tobacco) and/or in many other ways. A tobacco stream which is to be converted into the filler of a cigarette rod normally contains Virginia and/or Burley and/or Oriental tobacco and/or relatively small quantities of other tobaccos, and such stream can consist of shredded tobacco leaf laminae in the form of long and short shreds. In addition, the stream can contain fragments of puffed (expanded) tobacco ribs. Small quantities of tobaccos other than Virginia, Burley and Oriental are added to certain tobacco streams in order to influence the taste of tobacco smoke in a desired or special way.
Various constituents of a tobacco stream which is to be converted into a tobacco filler or into another smokers' product can greatly influence the taste, aroma as well as filling power of smokers' products. For example, depending upon their composition, the filing power of two tobacco streams can differ by as much as 80 percent. On the other hand, the filling power exerts a pronounced influence upon the quality of smokers' products. For example, the filling power of cigarettes can be a deciding factor (as far as the quality and acceptability of cigarettes is concerned) if tobaccos having different filling powers are used to turn out cigarettes having identical weights. In addition to filling power, homogeneousness of a tobacco stream is another important factor which must be taken into consideration in determining the quality of smokers' products. Thorough intermixing of all kinds of tobacco parts in a stream is desirable and advantageous in order to ensure that the characteristics of each of a short or long series of successively produced cigarettes will be identical or at least nearly identical. Homogeneousness or inhomogeneousness of a tobacco stream which is to be converted into the filler of a cigarette rod greatly influences the taste and hence the quality of cigarettes.
To summarize, two very important prerequisites for the making of smokers, products (e.g., cigarettes) of predetermined quality are satisfactory homogeneousness of the stream and satisfactory filling power. The importance of satisfactory homogeneousness will be readily appreciated by bearing in mind that even minor deviations of homogeneousness from a prescribed norm of a tobacco filler in a cigarette weighing between 700 and 1000 milligrams can entail readily detectable and highly undesirable departures from acceptable quality.
In spite of the aforedescribed importance of homogeneousness of a tobacco stream which is to be converted into the filler of a cigarette rod or into other smokers' products, heretofore tobacco mixing or homogenizing apparatus are far from satisfactory. For example, if tobacco parts are mixed in a standard long mixer (called silo) wherein layers of tobacco (e.g., layers having a width and length of 40 centimeters each) are placed next to and/or on top of each other on a mobile support to be engaged by a system of rakes which move up and down and transfer tobacco parts onto a conveyor, the quality of the mixture on the conveyor is often highly unsatisfactory and never entirely satisfactory. The combined width of several tobacco layers on the mobile support can be in the range of up to 3 meters, and the combined height of such plural layers can be in the range of up to and more than 1.5 meters. When the system of rakes is set in operation to remove tobacco particles from the front face of the assembly of tobacco layers on the mobile support, the elements of the raking system are likely to remove clumps, tufts or bunches of tobacco particles of the same type, i.e., the conveyor which receives the raked off tobacco parts carries an inhomogeneous tobacco stream. For example, if the assembly of tobacco layers contains a relatively small quantity of a particular tobacco type, particles of such particular type are likely to be admitted into the continuously moving stream at or close to 8-second intervals. Thus, the homogeneousness of the tobacco stream on the conveyor which serves to transport the tobacco stream to the next processing station (e.g., into a shredder) is highly unsatisfactory since the aforediscussed tobacco of a particular type will be present only in certain spaced-apart portions of the continuously moving stream. The homogeneousness of tobacco which forms the stream is not enhanced during further processing or is enhanced only to a very small or negligible extent. In other words, the aforementioned tufts, clumps or bunches of particles of the same type of tobacco are not spread out and distributed in the entire tobacco stream. Some mixing is likely to take place during treatment of tobacco particles in drums, driers, flavoring apparatus and certain other units through and/or on which the particles of tobacco must advance on their way toward the rod forming station in a cigarette making machine. Such minor mixing is not sufficient to ensure absolute or even substantial homogeneousness of tobacco in the stream prior to conversion into a rod-like filler.
The art is replete with disclosures of and proposals for machines and apparatus which can be utilized to homogenize accumulations of tobacco and/or other fibrous materials. However, presently known homogenizing machines and apparatus are not designed to spread out (i.e., to distribute) smaller accumulations (bunches, clumps or tufts) of particles of fibrous material in a manner which is acceptable for optimum treatment of tobacco in a cigarette rod making or a like machine. The reason is that heretofore known homogenizing apparatus operate on the principle of comminuting the material which, in the treatment of tobacco, is likely to be more harmful than beneficial as far as the ultimate products are concerned. Therefore, the makers of cigarettes and other smokers' products prefer to avoid the utilization of machines or apparatus which can promote homogenization but are likely to produce substantial quantities of so-called short tobacco, e.g., fragmentized shreds of tobacco leaf laminae. It follows that, in many if not most instances, the quality of cigarettes or other smokers' products is far from being acceptable or entirely satisfactory because the mixture of tobacco particles is likely to vary from cigarette to cigarette or from a short first series to the next series of successively produced cigarettes.